This invention relates in e, to the operation of hydraulically controllable downhole devices and in particular to a system and method for communicating hydraulic control from a tubing retrievable downhole device to a wireline retrievable downhole device.
One or more subsurface safety valves are commonly installed as part of the tubing string within oil and gas wells to protect against the communication of high pressure and high temperature formation fluids to the surface. These subsurface safety valves are designed to shut in production from the formation in response to a variety of abnormal and potentially dangerous conditions.
As one or more subsurface safety valves are built into the tubing string, these valves are typically referred to as tubing retrievable safety valves (xe2x80x9cTRSVxe2x80x9d). TRSVs are normally operated by hydraulic fluid pressure. The hydraulic fluid pressure is typically controlled at the surface and transmitted to the TRSV via a hydraulic fluid line. Hydraulic fluid pressure must be applied to the TRSV to place the TRSV in the open position. When hydraulic fluid pressure is lost, the TRSV will operate to the closed position to prevent formation fluids from traveling therethrough. As such, TRSVs are fail safe valves.
As TRSVs are often subjected to years of service in severe operating conditions, failure of TRSVs may occur. For example, a TRSV in the closed position may leak. Alternatively, a TRSV in the closed position may not properly open. Because of the potential for disaster in the absence of a properly functioning TRSV, it is vital that the malfunctioning TRSV be promptly replaced or repaired.
As TRSVs are typically incorporated into the tubing string, removal of the tubing string to replace or repair the malfunctioning TRSV is required. Depending on the circumstances, the cost of pulling the tubing string out of the wellbore can run into the millions of dollars.
It has been found, however, that a wireline retrievable safety valve (xe2x80x9cWRSVxe2x80x9d) may be inserted inside the original TRSV and operated to provide the same safety function as the original TRSV. These valves are designed to be lowered into place from the surface via wireline and locked in place inside the original TRSV. This method is a much more efficient and cost-effective alternative to pulling the tubing string.
If the WRSV is to take over the full functionality of the original TRSV, the WRSV must be communicated to the hydraulic control system. In traditional TRSVs, the communication path for the hydraulic fluid pressure to the replacement WRSV is established through a pre-machined radial bore extending from the hydraulic chamber to the interior of the TRSV. Once a failure in the TRSV has been detected, this communication path is established by shifting the TRSV to its locked out position and sheering a sheer plug that is installed within the radial bore.
It has been found, however, that operating conventional TRSVs to the locked out position and establishing this communication path has several inherent drawbacks. To begin with, the communication path creates a leak path for formation fluids up through the hydraulic control system. As noted above, TRSVs are intended to operate under abnormal well conditions and serve a vital and potentially life-saving function. Hence, if such an abnormal condition occurred when one TRSV has been locked out, even if other safety valves have closed the tubing string, high pressure formation fluids may travel to the surface through the hydraulic line. In addition, manufacturing a TRSV with this radial bore requires several high-precision drilling and thread tapping operations in a difficult-to-machine material. Any mistake in the cutting of these features necessitates that the entire upper subassembly of the TRSV be scrapped. The manufacturing of the radial bore also adds considerable expense to the TRSV, while at the same time reducing reliability of the finished product. For example, if the seal between the sheer plug and the radial bore fails, a communication path for formation fluids may be created between the annulus and the interior of the TRSV. Additionally, this added expense and complexity must be built into every installed TRSV, while it will only be put to use in some small fraction thereof.
Therefore, a need has arisen for a system and method for establishing a communication path for hydraulic fluid pressure to a WRSV from a failed TRSV. A need has also arisen for such a system and method that does not create the potential for formation fluids to travel up through the hydraulic control line. Further, a need has arisen for such a system and method that does not require the complexity, expense, leak potential and reliability concerns associated with manufacturing a TPSV with a radial bore having a sheer plug therein.
The present invention disclosed herein comprises a system and method for establishing a communication path for hydraulic fluid pressure to a wireline retrievable downhole device from a tubing retrievable downhole device. The system and method of the present invention avoids the potential for formation fluids to travel up through the hydraulic control line. The system and method of the present invention also avoids the complexity, expense, leak potential and reliability concerns associated with a pre-drilled radial bore in the tubing retrievable downhole device that requires a sheer plug to be disposed therein to provide a seal.
The system of the present invention for communicating hydraulic control from a tubing retrievable downhole device to a wireline retrievable downhole utilizes a tubing retrievable downhole device having a hydraulic chamber. After a malfunction of the tubing retrievable downhole device is detected and a need exists to otherwise achieve the functionality of the tubing retrievable downhole device, a radial cutting tool may be selectively located within the tubing retrievable downhole device. The radial cutting tool is used to create a fluid passageway between the hydraulic chamber of the tubing retrievable downhole device and the interior of the tubing retrievable downhole device. As such, hydraulic fluid may now be communicated down the existing hydraulic lines to the interior of the tubing. Once this communication path exists, the wireline retrievable downhole device may be positioned within the tubing retrievable downhole device such that the hydraulic fluid pressure from the hydraulic system may be communicated to the wireline retrievable downhole device.
The radial cutting tool that is selectively located within the tubing retrievable downhole device may be a chemical cutting tool, a mechanical cutting tool, explosive cutting mechanism or the like that are well known in the art.
In one embodiment of the present invention, the tubing retrievable downhole device may be a tubing retrievable safety valve that is operated to the lock out position prior to creating the fluid passageway between the hydraulic chamber of the tubing retrievable safety valve and the interior of the tubing retrievable safety valve. In this embodiment of the present invention, the wireline retrievable downhole device is typically a wireline retrievable safety valve that is used to replace the functionality of a malfunctioning tubing retrievable safety valve.
The method of the present invention for communicating hydraulic control from a tubing retrievable downhole device to a wireline retrievable downhole device involves locating a radial cutting tool within the tubing retrievable downhole device, creating a fluid passageway from the hydraulic chamber of the tubing retrievable downhole device to the interior of the tubing retrievable downhole device with the radial cutting tool and positioning the wireline retrievable downhole device within the tubing retrievable downhole device adjacent to the fluid passageway, thereby communicating hydraulic control to the wireline retrievable downhole device.
In the method of the present invention, the step of creating the fluid passageway may be achieved by chemically cutting the fluid passageway, mechanically cutting the fluid passageway, explosively cutting the fluid passageway or the like.
The method of the present invention may, for example, be used to communicate hydraulic fluid pressure to actuate a wireline retrievable safety valve that has been positioned within a tubing retrievable safety valve that has been operated to its lock out position.